1. Field of the Invention
The present invention relates to a stand assembly for supporting a monitor on a floor, and more particularly, to a stand assembly for a flat monitor for rotatably supporting the flat monitor.
2. Discussion of the Related Art
In general, in order to use flat monitors, such as LCD monitors, at desks or tables, stands for supporting the monitors are required. The stand is coupled to a backside of the monitor with a hinge assembly so that a user can adjust a tilting angle of the monitor to desired degrees.
A structure of related art monitor apparatus will be described briefly, with reference to FIG. 1.
There is a stand 3 at an upper end and a lower end thereof rotatably coupled to a monitor body 1 and a base 2 on a floor, with a monitor hinge 5 and a base hinge 6 respectively, thereby connecting the monitor body 1 and the base 2.
At opposite sides of the stand 3, there are one pair of parallel link members 7 for converting rotation of the stand 3 with respect to the base 2 to rotation of the monitor body 1. The link members 7 serve to rotate the monitor body 1 to a predetermined angle interlocked with rotation of the stand 3 with respect to a plane of the base 2. Of course, rotation of only the monitor body with respect to the stand is also possible.
The base hinge 6 is provided with a first base hinge 6a, and a second base hinge 6b, and the first base hinge 6a is provided with a torsion spring 6c for exerting an elastic force in a direction opposite to a downward rotation direction of the stand 3 toward the plane of base 2, to offset a torque generated by gravity of the monitor body 1.
Each of the first base hinge 6a and the monitor hinge 5 has a hinge shaft (not shown) inserted in an inserting hole therein, and engaged with an inside circumferential surface of the inserting hole with a predetermined friction, to support the torque generated by the gravity of the monitor body 1, too.
However, the related art monitor apparatus has the following problems.
When the user applies pressure to the monitor body in an upper or lower direction, the stand 3 rotates about the base hinge 6, to adjust a tilting angle of the stand 3 with respect to the base 1. In this instance, a tilting angle of the monitor body is adjusted by the link members, automatically. That is, at the time of tilting angle adjustment of the stand 3 with respect to the base 2, the tilting angle of the monitor body 1 with respect to the stand 3 is also adjusted automatically, and the present state is maintained.
Of course, if the monitor body 1 at a top or a bottom thereof is pushed backward, or pulled forward, the monitor body 1 rotates about the monitor hinge 5, to adjust the tilting angle of the monitor body 1 with respect to the stand 3 only.
However, since the related art monitor apparatus has the torque caused by the gravity of the monitor body 1 supported by the torsion spring 6c and friction of the hinge shaft (not shown), if the tilting angle θ of the stand 3 with respect to the base 2 is outside of a predetermined range of angle, since application of a working force is required, which is greater than a torque required for adjustment of the tilting angle of the monitor body, smooth adjustment of the tilting angle can not be achieved.
In more detail, referring to FIG. 2, the torque Tn required for supporting the monitor body 1 varies with the tilting angle θ following a locus of a curved line. However, the torque Ts available from the torsion spring 6c varies with the tilting angle θ following a locus of a straight line, and a total torque Ta available from the torsion spring 6c and friction of the hinge shaft (not shown) also varies following a locus of a straight line. This is because the torque Ts of the torsion spring is proportional to a spring constant and a torsion angle, and the friction is constant regardless of the tilting angle.
Therefore, in a case the tilting angle is smaller or greater than a certain range, the working force required varies with the tilting angle significantly due to a great difference between the required torque Tn and an actual available torque Ta, failing to achieve the smooth operation.